1. Field of the Invention
The present invention relates generally to the co-oligomerization of 1-dodecene and 1-decene and more particularly concerns the production of a polyalphaolefin having a kinetic viscosity at 100xc2x0 C. in the range of from about 4 to about 6 cSt, a Noack weight loss in the range of from about 4 to about 9%, a viscosity index in the range of from about 130 to about 145, and a pour point in the range of from about xe2x88x9260xc2x0 C. to about xe2x88x9250xc2x0 C.
2. Discussion of the Prior Arts
Oligomers of alpha olefins and their use as synthetic lubricants are well known. A large market exists for synthetic lubricants that have a viscosity in the range of from 4 to 6 cSt. A low Noack weight loss, a high viscosity index and a low pour point are also desired properties. The use of a hydrogenated oligomer as a synthetic lubricant depends to a large extent on the viscosity of the hydrogenated oligomer. Isoparaffinic oils with kinetic viscosities at 100xc2x0 C. in the range of from 4 to 6 cSt that are used as synthetic lubricant base stocks, are typically made by oligomerization of 1-decene using a BF3 catalyst and an alcohol promoter. The range of properties for these polyalphaolefins generally include a kinematic viscosity in the range of 4 to 6 cSt at 100xc2x0 C., a Noack weight loss in the range of about 6 to 15%, a viscosity index in the range of 120-135, and a pour point of less than xe2x88x9255xc2x0 C.
It is possible to prepare a polyalphaolefin with a kinematic viscosity at 100xc2x0 C. of 5 cSt with a better viscosity index and Noack weight loss by using 1-dodecene instead of 1-decene as the raw material for such base stocks. When 1-dodecene is used as the raw material, the isoparaffinic oil so prepared typically has a Noack weight loss of 5.5% to 7% and a viscosity index of 143 but a pour point of only xe2x88x9245xc2x0 C. to about xe2x88x9250xc2x0 C. Another drawback to the use of 1-dodecene as the raw material is that it does not permit the product of isoparaffinic oils having viscosity below 5 cSt without an unacceptably high Noack weight loss. For instance, an isoparaffinic oil having a 4.5 cSt kinematic viscosity could be prepared by blending a 5 cSt oil made from 1-dodecene with a 4 cSt oil made from 1-decene, but the blend would have a Noack weight loss of 10-11%. Furthermore, using pure 1-dodecene as the raw material in a typical synthesis generally affords large amounts of heavier co-product besides the desired 4-6 cSt material. For example, typically about 70% of a 7 cSt isoparaffinic oil is produced in addition to the desired 5 cSt isoparaffinic oil.
Consequently, it is highly desirable to be able to prepare an isoparaffinic oil base stock having a kinematic viscosity of 4 to 6 cSt at 100xc2x0 C. and a Noack weight loss in the range of about 4 to about 9%, a viscosity index in the range of from about 130 to about 145 and a pour point in the range of xe2x88x9260xc2x0 to xe2x88x9250xc2x0 C. It is also highly desirable to reduce the amount of the aforesaid heavier co-products.
One possible approach may be to use mixtures of 1-olefins as the raw material. DiLeo et al., U.S. Pat. No. 4,950,822 discloses in column 2 lines 63-66 that optimally mixtures of alpha-olefins such as 1-octene, 1-decene and 1-dodecene can be used to arrive at an isoparaffinic oil product having a viscosity suitable for use in an internal combination engine, but does not elaborate further or illustrate that point. Cupples et al., U.S. Pat. Nos. 4,045,507 and 4,045,508 discloses oligomerization processes that are useful with mixtures of 1-olefins as the feed, particularly mixtures of 1-decene with up to about 50 mole percent of 1-octene and/or 1-dodecene.
Thus far no one has disclosed an oligomerization process employing 1-dodecene as a co-monomer for producing an isoparaffinic oil base stock having a kinematic viscosity in the range of from 4 to 6 at 100xc2x0 C., a Noack weight loss in the range of from about 4 to about 9%, a viscosity index in the range of from about 130 to about 145, and a pour point in the range of from about xe2x88x9260xc2x0 to about xe2x88x9250xc2x0 C.
It is therefore a general object of the present invention to provide an improved ligomerization process employing 1-dodecene and 1-decene as a co-monomer that overcomes the aforesaid problems and meets the aforesaid objectives.
More particularly, it is an object of the present invention to provide an improved aforesaid oligomerization process that produces a product having a kinematic viscosity of from about 4 to about 6 at 100xc2x0 C., a Noack weight loss of from about 4% to about 9%, a viscosity index of from about 130 to about 145, and a pour point in the range of from about xe2x88x9260xc2x0 to about xe2x88x9250xc2x0 C.
It is another object of the present invention to provide an improved aforesaid process that minimizes the amount of heavier byproduct that is produced in addition to the aforesaid product having a kinematic viscosity in the range of from about 4 to about 6.
Other objects and advantages will become apparent upon reading the following detailed description and appended claims.
These objects are achieved by the process of the present invention for the production of a polyalphaolefin product, comprising co-oligomerizing a mixture comprising from about 60 to about 90 weight percent of 1-dodecene and from about 10 to about 40 weight percent of 1-decene in the presence of a BF3 catalyst and an alcohol promoter at a temperature in the range of from about 20xc2x0 C. to about 60xc2x0 C. to thereby form a polyalphaolefin having a kinematic viscosity at 100xc2x0 C. in the range of from about 4 to about 6 cSt, a Noack weight loss in the range of from about 4 to about 9%, a viscosity index in the range of from about 130 to about 145 and a pour point in the range of from about xe2x88x9260xc2x0 C. to about xe2x88x9250 xc2x0 C.
The feedstock for the method of the present invention is a mixture of 1-dodecene and 1-decene. The feedstock is comprised of from about 60% to about 90%, preferably to about 70%, by weight of 1-dodecene and from about 10% to about 40%, preferably to about 30%, by weight of 1-decene.
Preferably, 1-decene is added portionwise during the conduct of the oligomerization. Preferably at least 50%, and more preferably at least 90% by weight of the total amount of the 1-decene employed in the oligomerization is introduced into the reaction mixture containing 1-dodecene and the pressurized atmosphere of boron trifluoride as the oligomerization reaction proceeds. The balance, if any, of the 1-decene is charged to the reactor before commencing the oligomerization reaction. The portionwise feed can be effected by feeding portions of the total 1-decene charge as a series of individual increments over a period of time. In this case the 1-decene is introduced to the reaction mixture as a discontinuous series of small additions until the predetermined amount to be employed pursuant to this invention has been introduced into the oligomerization mixture. Alternatively, and preferably, the feed of 1-decene to the oligomerization mixture is conducted slowly and continuously until the total predetermined amount of the 1-decene has been added. In either case the 1-decene feed rate should be from about 400 parts, preferably from about 600 parts, to about 800 parts by weight of 1-decene per 1000 parts by weight of 1-dodecene and 1-decene per hour.
The boron trifluoride atmosphere within the reactor is typically maintained at a gauge pressure within the range of 1 to 4 bars including 0.05 to 1.5 bars of nitrogen. A preferred pressure range is from 2 to 3 bars gauge with 1 bar (gauge) of nitrogen. Reaction temperatures used in the process are normally in the range of from 20xc2x0 C. to 60xc2x0 C. and preferably 35xc2x0 C. Alcohol promoters that can be used include alkanols having up to about 18 carbon atoms, and preferably up to about 12 carbon atoms, such as, for example, ethanol, 1-propanol, 1-butanol, 2-methylpropanol, 1-pentanol, 1-hexanol, 1-octanol, 2-ethyl-1-hexanol and 1-decanol. Most preferably, the alcohol employed has up to 6 carbon atoms. The most preferred alcohol is 1-butanol. Diols and other polyols can also be used, but are less preferred. One alcohol or a mixture of alcohols can be used as the alcohol promoter. The most preferred mixture of alcohol promoters is a mixture of ethanol and 1-butanol. Preferably more 1-butanol than ethanol is employed, and most preferably a 3:1 weight ratio of 1-butanol to ethanol is employed. The total amount of alcohol promoter employed varies from about 3 to 7 parts per 1000 parts by weight of 1-dodecene and 1-decene with most preferably about 5 parts of alcohol promoter per 1000 parts by weight of 1-dodecene and 1-decene.
Preferably the alcohol catalyst promoter is introduced into the reaction system on a portionwise basis. Preferably at least 50%, more preferably at least 70%, and most preferably at least 90% by weight of the total amount of the alcohol promoter employed is introduced into the reaction mixture as the oligomerization reaction proceeds. The balance, if any, of the alcohol promoter is introduced to the reaction mixture before commencing the oligomerization reaction. The portionwise addition of the alcohol promoter can be effected by feeding portions of the total alcohol charge as a series of individual increments over a period of time. In this case the alcohol promoter is introduced to the reaction mixture as a discontinuous series of small additions until the predetermined amount to be employed pursuant to this invention has been introduced into the oligomerization mixture. Alternatively, and preferably, the feed of alcohol promoter to the oligomerization mixture is conducted slowly and continuously until the total predetermined amount of the alcohol has been added. In either ease the alcohol feed rates should be from 0.8 to 4 parts by weight of alcohol per 1000 parts by weight of 1-dodecene and 1-decene per hour, preferably from 1 to 3 parts of alcohol promoter per 1000 parts by weight of 1-dodecene and 1-decene per hour, and most preferably from 2 to 3 parts of alcohol promoter per 1000 parts by weight of 1-dodecene and 1-decene per hour.
The reaction time needed to effect more than 95% monomer conversion depends on the total amount of alcohol promoter used and on the ratio of 1-decene to 1-dodecene. The higher the relative amount of alcohol promoter is and the more 1-decene employed, the lower the reaction time is. The reaction time for 95% conversion typically varies between 1 and 2 hours.